Linux includes a few privileged processes called kernel threads. Is there any scheduler which runs/suspends them? If yes, is this scheduler the same as the system scheduler (I mean the one to schedule the whole system processes)?
0
votes
2 Answers
1
votes
The Linux scheduler is scheduling tasks. These can be
- kernel threads (e.g.
kswapd), or - single-threaded processes (e.g.
bash), or - individual threads of a multi-threaded process (e.g. some browsers or servers)
The many threads of a multi-threaded process are tasks sharing a common address space (and other things, e.g. file descriptors).
AFAIK, the scheduler does not separate kernel threads from other tasks. But the scheduler do take into account scheduling policies (sched_setscheduler(2)) and priorities (setpriority(2)) (For most kernel threads, the priority is often very high). See sched(7)
1
votes
Yes ! Let me clarify the system scheduler part here.
Every task is associated with a task_struct which contains the details of each task say its pid, its name, when it recently started, priority etc etc.http://lxr.free-electrons.com/source/include/linux/sched.h#L1224
Typically depending on the priority of the task either Fair scheduler or Real time scheduler kicks in and these co exist. Just to keep it simple and not to go into details, these are different scheduler algorithms that cater to different type of tasks.
Now Kernel threads also have an associated task_struct and as @Basile Starynkevitch pointed a couple of KPI's, we can use sched_setparam KPI's to modify the sched params and change the scheduler to which the task belongs to depening on what they are about to do.
